Many motor vehicle engines, whether compression ignition or spark ignition engines, are provided with electronic fuel injection systems to satisfy the need for precise and reliable fuel delivery into the cylinders of the engines. Such precision and reliability are demanded to address the goals of increasing fuel efficiency, maximizing power output, and controlling undesirable products of combustion.
Several electronic fuel injection systems designed for internal combustion engines use a mechanical linkage from the engine to pressurize the fuel charge. Using mechanical pressurization, an extremely high injection pressure, now often exceeding 20,000 psi (13,800 Newtons per square centimeter) and occasionally reaching a transient peak value of 23,500 psi (16,200 Newtons per square centimeter), is developed within the timing chamber of the injector. A higher fuel injection pressure provides a cleaner exhaust because particulate emissions are reduced, and so is desirable to meet the tightened emission standards which are being and will be imposed on motor vehicles.
One problem preventing the achievement of higher injection pressures in a practical engine is premature failure of the injector body when such pressures are applied. Some bores of the body are exposed to the full preinjection and injection pressure, as well as the high mechanical stresses of moving parts in the injector. The typical life of an injector body is unacceptably reduced when fuel injection pressures exceeding 20,000 psi (13,800 Newtons per square centimeter) are routinely applied within the timing chamber.
Electrochemical machining is a known method for forming workpieces, particularly metal workpieces. A conventional electrochemical machining head comprises a supply of an electrically conductive fluid for application to the workpiece, electrodes communicating with the fluid supply and workpiece for creating an electrical current between the fluid and the workpiece, and a mask for confining the flow of the fluid to the material of the workpiece to be removed. Electrochemical machining has not been employed to address the problem of fuel injector body failure resulting from high fuel injection pressure.